Flexible dental prosthesis



June 27, 1$7 R. M. CROW FLEXIBLE DENTAL PROSTHESIS Filed April 12, 1965 INVENTOR- Aoc/mey M. C/Or/V TY'OPNE 3 United States Patent "ice 3,327,392 FLEXIBLE DENTAL PROSTHESIS Rodney M. Crow, Fort Worth, Tex., assignor to Dow Corning Corporation, Midland, Mich., a corporation of Michigan Filed Apr. 12, 1965, Ser. No. 447,404 3 Claims. (Cl. 32-2) This application is a continuation-in-part of copending US. application Ser. No. 386,025, filed July 29, 1964, now abandoned.

The present invention relates to artificial dentures and more particularly to new and useful types of artificial dentures.

Dental prosthesis have heretofore been made of various relatively hard and rigid materials, including for example, acrylics, styrene, vulcanite, metals and porcelain. These materials exhibit several disadvantageous characteristics', including discomfort to the wearer due to friction and surface hardness. Additionally, these materials are subject to cracking and/ or breakage because of their extreme rigidity. Furthermore, natural teeth have a certain amount of limited movement and shock absorption. These characteristics were completely lacking in prior art dental prosthesis. While various types of denture liners of soft material have been suggested, none has proven to be completely satisfactory.

An object of the present invention, therefore, is to provide an improved artificial denture which more nearly duplicates the function and comfort of natural healthy teeth.

A further object is the provision of an artificial denture made of a material which is pliable and easily tolerated by the tissue of the mouth of the wearer, thereby increasing comfort to the wearer.

A still further object is to provide for use in artificial dentures a material to which artificial teeth would readily bond and into which teeth could be individually set, thereby eliminating any necessity for tying teeth together and allowing greater individual tooth movement and shock absorption.

In accordance with the present invention these and other objects are acomplished by fabricating artificial dentures from mixtures of elastomeric silicones with commercially available types of denture base compositions including, for example, acrylic and vinyl resins, and polystyrenes and mixtures thereof. It has been found that the silicone room temperature vulcanizing elastomers blend readily with these normally rigid denture base materials to form a flexible base having sufiicient strength and wear characteristics for use in dentures, although the silicone material by itself is too soft for practical use. The method may be applied to fabrication of either full or partial artificial dentures and is characterized by the formation of a gum fitting base exclusively of pliable, elastic material and having all of the other requisite properties compatible with its installation in the mouth of a dental patient.

Other objects and attendant advantages of the present invention will become readily apparent to those skilled in the art by a consideration of the following detailed description when read in connection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of an artificial denture in its final stage of fabrication in accordance with the present invention;

FIG. 2 is a perspective view of an artificial tooth modified for use in the denture fabricating method of the present invention; and

FIG. 3 is a cross-sectional view of the tooth of FIG. 2 in a further stage of processing.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts through- Patented June 27, 1967 out the several views, there is shown in FIG. 1 a denture, generally designated by the reference numeral 10, mounted on an artificial stone casting 12. The stone casting 12 is made from an impression taken of either the upper or lower portion of the patients mouth and is embedded in plaster 14 to form one-half of a mold formed within the flask portion 16 in the manner well-known in the art.

The artificial denture 10-is mounted on the simulated gum surface 18 of the casting from which it may be removed in the final stage of fabrication for polishing purposes. The denture is formed from a tooth carrying base 20 contoured by the fabrication method to fit the gum surfaces of the patient and the artificial teeth 22 are embedded therein. Each tooth is made of hard, rigid materials such as plastics as is known in the art.

Although the teeth 22 are made of materials which are conventional in the art, the tooth carrying base 20 is, in accordance with the present invention, made exclusively of a material which is more desirably pliable and yet elastic so that it returns to its original shape when deformed. This material of course, must also have all of the properties necessary for use as a denture base and for compatibility with the environmental conditions within a persons mouth. These criteria require sufficient strength to hold the artificial teeth in position, and sufficient rigidity to keep the denture in place in the mouth while chewing. They also require a material which is chemically inert with respect to any foods, odorless, tasteless, easily cleaned, abrasion resistant, stain resistant, has low water absorption and satisfactory tissue tolerance, and is of stable consistency, besides being soft and elastic in nature sometimes including fluorosilicones. They may be of either the one component or two component type, although one component rubbers are generally preferred since they do not require mixing prior to use. Such materials are known to those skilled in the art and need not be discussed here in great detail. Examples of suitable room temperature vulcanizable silicon rubbers are described in US. Patents No. 2,927,907; 3,035,016; 3,061,567; and 2,833,742. For obvious reasons, only medical grade materials should be employed. Particular success has been found by the use of room temperature vulcanizing silicone rubber sold by the Dow Corning Corporation under the name Silastic 390.

The term acrylic is employed herein to cover any of the conventional denture base materials presently used to make rigid dentures, including polymers of any ester, nitrile or amide, of acrylic, methacrylic or ethacrylic acids. Generally speaking, methyl methacrylate is the primary constituent of such materials. However, these materials may also contain polystyrene, polyvinyl chloride, polyvinyl acetate and other polymers and monomers. Numerous materials of this type are known in the art and are described in the literature so need not be described in detail herein.

The ratio of acrylic to silicone elastomer may be varied between 6 to 1 and 1 to 10 by volume with varying degrees of success. The preferred mixture is a ratio of one part acrylic to three parts silicone elastomer. Ratios of acrylic to silicone greater than 6 to 1 create a material which is too rigid to bend and is easily cracked. Ratios smaller than 1 to 10 are far too flexible and lack sufficient strength to hold teeth in the denture in use.

The ingredients are thoroughly mixed, in the manner used heretofore when acrylics were used alone, and the mixture is used to fill the mold cavity. The mixture is then cured within the flask forming a denture base possessing a substantially softer surface than acrylic materials and having the desired elastic property and compatability with oral tissues.

To fabricate the denture in accordance with the present invention, a selection is made of the proper mold and toothshade using conventional artificial teeth. After the artificial stone models of the mouth are obtained from impression these models are waxed up and the teeth set into the wax, after which the models are mounted on a conventional articulator in order to accurately set the teeth and perfect the occulsion and excursions of movement. After final refinement of the waxed model a mold is formed in the usual manner well known by this skilled in the art. The wax is then boiled out or otherwise removed so as to form a mold cavity between the mold sections into which the curable material is placed in order to form the denture base. One-half of the mold thus formed is shown in FIG. 1, the other half forming the remainder of the cavity from which the base is cast as well as the recesses which hold the artificial teeth after the wax is removed from the cavity.

Before the material forming the base is introduced into the mold for curing, the teeth are removed and prepared in accordance with the present invention for bonding to the denture base. As shown in FIG. 2, each tooth includes an exposed portion 24 and an embedded portion 26 which projects in to the mold cavity so that it may be embedded in the material of the denture base 20. The portion 26 is drilled to provide a plurality of perforations 28 on all surfaces thereof.

After drilling, the tooth 22 is packed with the acrylicsilicone denture base material 30, as shown in FIG. 3, to ensure that the perforations are all filled by the material. The packed tooth is then reinserted into its mold section with the packed portion 30 extending into the mold cavity. The mold cavity is then filled with the denture base material and the mold sections are clamped shut. The denture is then allowed to cure. To speed curing, the mold containing the denture may be placed in boiling water as has been done heretofore with acrylics. After curing the mold, flask sections are separated and the completed denture is given a final polish in the conventional manner.

In use, the comfort to the patient produced by the present invention, as compared to that obtained with dentures using conventional acrylics, has'been found to be quite significant. The denture has the requisite strength and forms a chemical and physical bond between the base and the artificial teeth, thereby avoiding the necessity for any anchoring elements or base regidifying members. The fabrication method is also thereby simplified.

Obviously, many modifications and variations of the present invention will become obvious to those skilled in ther art from a consideration of the foregoing description of a preferred embodiment of the invention. It is therefore to be understood that Within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

That which isclaimed is:

1. An artificial denture comprising:

a denture base member consisting of pliable, elastic material contoured to fit adjacent to gum surfaces of the wearer,

said denture base comprising a uniform mixture of acrylic material and silicone elastomeric material, and

at least one rigid artificial tooth having a portion embedded in said denture base.

2. An artificial denture as defined in claim 1 wherein the embedded portion of said artificial tooth is perforated for physical bonding to said denture base and said denture base includes portions thereof extending into the perforations in said tooth.

3. An artificial denture as defined in claim 2 wherein said mixture of acrylic material and silicone elastomeric material comprises a ratio of acrylic to silicone elastomer between 6 to 1 and 1 to 10 by'volume.

References Cited UNITED STATES PATENTS 2,659,106 11/1953 Leicht 322 X 2,770,880 11/1956 Sherrod 322 3,083,459 4/1963 McMurry et al. 32-2 3,258,509 6/1966 Barnhart 264-17 FOREIGN PATENTS 1,109,832 6/1961 Germany.

RICHARD A. GAUDET, Primary Examiner.

ROBERT E. MORGAN, Examiner. 

1. AN ARTIFICAL DENTURE COMPRISING: A DENTURE BASE MEMBER CONSISTING OF PLIABLE, ELASTIC MATERIAL CONTOURED TO FIT ADJACENT TO GUM SURFACES OF THE WEARER, SAID DENTURE BASE COMPRISING A UNIFORM MIXTURE OF ACRYLIC MATERIAL AND SILICONE ELASTOMERIC MATERIAL, AND 